Unclassified white matter disorders: A diagnostic journey requiring close collaboration between clinical and laboratory services.

BACKGROUND: Next generation sequencing studies have revealed an ever-increasing number of causes for genetic disorders of central nervous system white matter. A substantial number of disorders are identifiable from their specific pattern of biochemical and/or imaging findings for which single gene testing may be indicated. Beyond this group, the causes of genetic white matter disorders are unclear and a broader approach to genomic testing is recommended. AIM: This study aimed to identify the genetic causes for a group of individuals with unclassified white matter disorders with suspected genetic aetiology and highlight the investigations required when the initial testing is non-diagnostic. METHODS: Twenty-six individuals from 22 families with unclassified white matter disorders underwent deep phenotyping and genome sequencing performed on trio, or larger, family groups. Functional studies and transcriptomics were used to resolve variants of uncertain significance with potential clinical relevance. RESULTS: Causative or candidate variants were identified in 15/22 (68.2%) families. Six of the 15 implicated genes had been previously associated with white matter disease (COL4A1, NDUFV1, SLC17A5, TUBB4A, BOLA3, DARS2). Patients with variants in the latter two presented with an atypical phenotype. The other nine genes had not been specifically associated with white matter disease at the time of diagnosis and included genes associated with monogenic syndromes, developmental disorders, and developmental and epileptic encephalopathies (STAG2, LSS, FIG4, GLS, PMPCA, SPTBN1, AGO2, SCN2A, SCN8A). Consequently, only 46% of the diagnoses would have been made via a current leukodystrophy gene panel test. DISCUSSION: These results confirm the importance of broad genomic testing for patients with white matter disorders. The high diagnostic yield reflects the integration of deep phenotyping, whole genome sequencing, trio analysis, functional studies, and transcriptomic analyses. CONCLUSIONS: Genetic white matter disorders are genetically and phenotypically heterogeneous. Deep phenotyping together with a range of genomic technologies underpin the identification of causes of unclassified white matter disease. A molecular diagnosis is essential for prognostication, appropriate management, and accurate reproductive counseling.

Acute flaccid myelitis in childhood: a retrospective cohort study.

BACKGROUND AND PURPOSE: Clusters of acute limb weakness in paediatric patients have been linked to outbreaks of non-polio enteroviruses, termed acute flaccid myelitis (AFM). Outside these clusters, in countries where polio is not endemic, this poliomyelitic-like illness is rare in childhood and its natural history is not well defined. We describe presenting features, investigation findings and long-term outcome of a series of children with AFM. METHODS: This was a retrospective cohort study. RESULTS: Eight children (six females) aged 3 months to 8 years (median age 5 years) met case criteria. Initial symptoms were pain (n = 7) followed by limb weakness with hypotonia (n = 8). Flaccid paralysis occurred in only three patients. Two had cranial nerve dysfunction. Magnetic resonance imaging of the spinal cord demonstrated grey matter involvement particularly affecting the anterior cord, with longitudinally extensive changes in three children. Cerebrospinal fluid examination showed pleocytosis in six children with raised cerebrospinal fluid protein in five. Nerve conduction and electromyography findings were consistent with a motor neuronopathy. Residual deficits were common, with moderate to severe weakness seen in five patients. Median follow-up was 28 months (range 17-108 months, 30.4 patient years in total). CONCLUSIONS: Acute flaccid myelitis is an uncommon condition in childhood with a high rate of significant long-term morbidity. AFM should be considered in children presenting with acute limb pain and weakness.

Observations of body mass index in Duchenne muscular dystrophy: a longitudinal study.

BACKGROUND/OBJECTIVES: Nutritional issues that are associated with Duchenne muscular dystrophy (DMD) remain poorly understood. The aim of this analysis was to describe and explore longitudinal observations of body mass index (BMI) in a cohort of children with DMD. SUBJECTS/METHODS: Anthropometric and clinical characteristics were collected retrospectively and longitudinally for boys with DMD seen in two large neuromuscular clinics. BMI Z-scores were determined using the Centers for Disease Control and Prevention reference values for children (2000). RESULTS: Medical records (n=193) were examined from which 75% were included for analysis. The mean age of the cohort at the time of data collection was 11.9 years, with 72% of patients currently or previously using steroids. The highest prevalence of obesity based on the BMI Z-score was 50% at the age of 10 years. Longitudinally, BMI Z-scores from the age of 2 to 12 years plot approximately one s.d. above the mean, after which there is a marked and progressive decline. BMI gainers were identified for whom BMI Z-score increased by 1.65 units compared with the 0.09 units in non-gainers. BMI gainers were younger when they had their first BMI measurement (5.9 vs 7.2 years), and this measure was significantly lower compared with the non-gainers (BMI Z-score: 0.04 vs 1.17). In this cohort, BMI was associated with age, ambulatory status and lung function. CONCLUSIONS: This study demonstrates that boys with DMD using steroid therapy experience shifts in BMI. A declining BMI appears to be associated with increasing age. Interpretation of growth patterns is limited here by a lack of normative growth references in DMD.

Randomized, blinded trial of weekend vs daily prednisone in Duchenne muscular dystrophy.

OBJECTIVE: To perform a double-blind, randomized study comparing efficacy and safety of daily and weekend prednisone in boys with Duchenne muscular dystrophy (DMD). METHODS: A total of 64 boys with DMD who were between 4 and 10 years of age were randomized at 1 of 12 centers of the Cooperative International Neuromuscular Research Group. Efficacy and safety of 2 prednisone schedules (daily 0.75 mg/kg/day and weekend 10 mg/kg/wk) were evaluated over 12 months. RESULTS: Equivalence was met for weekend and daily dosing of prednisone for the primary outcomes of quantitative muscle testing (QMT) arm score and QMT leg score. Secondary strength scores for QMT elbow flexors also showed equivalence between the 2 treatment groups. Overall side effect profiles of height and weight, bone density, cataract formation, blood pressure, and behavior, analyzed at 12 months, did not differ between weekend and daily dosing of prednisone. CONCLUSIONS: Weekend dosing of prednisone is equally beneficial to the standard daily dosing of prednisone. Analysis of side effect profiles demonstrated overall tolerability of both dosing regimens. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that weekend prednisone dosing is as safe and effective as daily prednisone in preserving muscle strength and preventing body mass index increases in boys with DMD over a 12-month period.

CD45 fraction bone marrow cells as potential delivery vehicles for genetically corrected dystrophin loci.

Targeted correction of mutations in muscle can be delivered by direct i.m. injection of corrective DNA to the dystrophic muscle or by autologous injection of cells that have been genetically corrected after isolation from the individual with the dystrophic muscle. The successful application of chimeraplasty and short fragment homologous replacement to correct the exon 23 nonsense mdx transition at the mouse dys locus has opened up the possibility that with further development, targeted gene correction may have some future application for the treatment of muscular dystrophies. In vitro, application of targeted gene correction at the mdx dys locus results in better correction efficiencies than when applied directly to dystrophic muscle. This suggests that at least for the time being, a strategy involving ex vivo correction may be advantageous over a direct approach for delivery of gene correction to dystrophic muscle. This, particularly in view of recent developments indicating that bone-marrow-derived cells are able to systemically remodel dystrophic muscle, whilst penetration of DNA introduced to muscle is limited to individually injected muscles. Application of targeted gene correction to Duchenne dystrophy needs to account for the fact that about 65% of Duchenne muscular dystrophy cases involve large frame-shift deletion of gene sequence at the dys locus. Traditionally, whilst targeted gene correction is able to restore point mutations entirely, it remains to be seen as to whether a strategy for the 'correction' of frame shift deletions may be engineered successfully. This communication discusses the possibility of applying targeted gene correction to dystrophic muscle in Duchenne dystrophy.

Targeted gene correction in the mdx mouse using short DNA fragments: towards application with bone marrow-derived cells for autologous remodeling of dystrophic muscle.

In muscle, mutant genes can be targeted and corrected directly by intramuscular (i.m.) injection of corrective DNA, or by ex vivo delivery of DNA to myogenic cells, followed by cell transplantation. Short fragment homologous replacement (SFHR) has been used to repair the exon 23 nonsense transition at the Xp21.1 dys locus in cultured cells and also, directly in tibialis anterior from male mdx mice. Whilst mdx dys locus correction can be achieved in up to 20% of cells in culture, much lower efficiency is evident by i.m. injection. The major consideration for application of targeted gene correction to muscle is delivery throughout relevant tissues. Systemically injected bone marrow (BM)-derived cells from wt C57BL/10 ScSn mice are known to remodel mdx muscle when injected into the systemic route. Provided that non muscle-derived cell types most capable of muscle remodeling activity can be more specifically identified, isolated and expanded, cell therapy seems presently the most favorable vehicle by which to deliver gene correction throughout muscle tissues. Using wt bone marrow as a model, this study investigates systemic application of bone marrow-derived cells as potential vehicles to deliver corrected (ie wt) dys locus to dystrophic muscle. Intravenous (i.v.) and intraperitoneal (i.p.) injections of wt BM were given to lethally and sub-lethally irradiated mdx mice. Despite both i.v. and surviving i.p. groups containing wt dys loci in 100% and less than 1% of peripheral blood nuclei, respectively, both groups displayed equivalent levels of wt dys transcript in muscle RNA. These results suggest that the muscle remodeling activity observed in systemically injected BM cells is not likely to be found in the hemopoietic fraction.

Anti-myelin associated glycoprotein antibodies: variability in patterns of IgM binding to peripheral nerve.

We previously found that serums with anti-sulfatide antibodies have several different patterns of binding to neural tissue. In this study, we asked whether serums with anti-myelin associated glycoprotein (MAG) antibodies also have similar variations in patterns of tissue binding. We examined binding to peripheral nerve in 49 serums with IgM anti-MAG antibodies and 13 serums with IgM anti-sulfoglucuronyl paragloboside (SGPG) antibodies but no MAG binding. We correlated patterns of binding with titers of IgM binding to MAG and SGPG measured by ELISA methods. Our results show that IgM in most anti-MAG serums stained areas of non-compact myelin, including the periaxonal and outer myelin membranes and Schmidt-Lanterman incisures. However, other patterns included IgM binding to areas of compact myelin and to non-myelin structures including axons and endoneurial macrophages. IgM in anti-SGPG serums bound to axons or macrophages, but rarely to myelin-related structures. A total of 11/62 (18%) of serums had IgM binding to axons, six with anti-MAG antibodies and five with anti-SGPG antibodies. The majority of these serums (73%) had SGPG titers greater than MAG titers when measured by ELISA. We conclude that anti-MAG serums have several different binding patterns to neural tissue, including axonal binding, especially when anti-MAG antibodies cross-react with SGPG. These different binding patterns may relate to the ability of anti-MAG serum IgM to bind both MAG and SGPG or to other molecules with a sulfated glucuronic acid epitope that are present in peripheral nerve.

In vivo and in vitro correction of the mdx dystrophin gene nonsense mutation by short-fragment homologous replacement.

Targeted genetic correction of mutations in cells is a potential strategy for treating human conditions that involve nonsense, missense, and transcriptional splice junction mutations. One method of targeted gene repair, single-stranded short-fragment homologous replacement (ssSFHR), has been successful in repairing the common deltaF508 3-bp microdeletion at the cystic fibrosis transmembrane conductance regulator (CFTR) locus in 1% of airway epithelial cells in culture. This study investigates in vitro and in vivo application of a double-stranded method variant of SFHR gene repair to the mdx mouse model of Duchenne muscular dystrophy (DMD). A 603-bp wild-type PCR product was used to repair the exon 23 C-to-T mdx nonsense transition at the Xp21.1 dys locus in cultured myoblasts and in tibialis anterior (TA) from male mdx mice. Multiple transfection and variation of lipofection reagent both improved in vitro SFHR efficiency, with successful conversion of mdx to wild-type nucleotide at the dys locus achieved in 15 to 20% of cultured loci and in 0.0005 to 0.1% of TA. The genetic correction of mdx myoblasts was shown to persist for up to 28 days in culture and for at least 3 weeks in TA. While a high frequency of in vitro gene repair was observed, the lipofection used here appeared to have adverse effects on subsequent cell viability and corrected cells did not express dystrophin transcript. With further improvements to in vitro and in vivo gene repair efficiencies, SFHR may find some application in DMD and other genetic neuromuscular disorders in humans.

Nemaline myopathy caused by mutations in the muscle alpha-skeletal-actin gene.

Nemaline myopathy (NM) is a clinically and genetically heterogeneous disorder characterized by muscle weakness and the presence of nemaline bodies (rods) in skeletal muscle. Disease-causing mutations have been reported in five genes, each encoding a protein component of the sarcomeric thin filament. Recently, we identified mutations in the muscle alpha-skeletal-actin gene (ACTA1) in a subset of patients with NM. In the present study, we evaluated a new series of 35 patients with NM. We identified five novel missense mutations in ACTA1, which suggested that mutations in muscle alpha-skeletal actin account for the disease in approximately 15% of patients with NM. The mutations appeared de novo and represent new dominant mutations. One proband subsequently had two affected children, a result consistent with autosomal dominant transmission. The seven patients exhibited marked clinical variability, ranging from severe congenital-onset weakness, with death from respiratory failure during the 1st year of life, to a mild childhood-onset myopathy, with survival into adulthood. There was marked variation in both age at onset and clinical severity in the three affected members of one family. Common pathological features included abnormal fiber type differentiation, glycogen accumulation, myofibrillar disruption, and "whorling" of actin thin filaments. The percentage of fibers with rods did not correlate with clinical severity; however, the severe, lethal phenotype was associated with both severe, generalized disorganization of sarcomeric structure and abnormal localization of sarcomeric actin. The marked variability, in clinical phenotype, among patients with different mutations in ACTA1 suggests that both the site of the mutation and the nature of the amino acid change have differential effects on thin-filament formation and protein-protein interactions. The intrafamilial variability suggests that alpha-actin genotype is not the sole determinant of phenotype.

Clinical and neuroradiologic features of acute disseminated encephalomyelitis in children.

OBJECTIVE: To identify the clinical and neuroradiologic features of acute disseminated encephalomyelitis (ADEM) in childhood. METHODS: A retrospective review was conducted of the medical records and MRI of children who presented to the Royal Children's Hospital in Melbourne with ADEM between January 1993 and December 1998. RESULTS: Of the 31 patients included in this study, 22 (71%) experienced a prodromal illness. Two patients (6%) had received hepatitis B vaccine 3 to 6 weeks before developing their illness. Symptoms and signs typically evolved over several days. Ataxia was the most common presenting feature, occurring in 20 patients (65%). MRI findings were variable, but lesions were most commonly seen bilaterally and asymmetrically in the frontal and parietal lobes. The authors found a high incidence of the corpus callosal and periventricular changes more typically associated with MS, but they also found a high rate of deep gray matter involvement (61% of patients). The use of high-dose IV methylprednisolone was usually associated with rapid recovery. Eighty-one percent of patients recovered completely, with only mild sequelae recorded in the remaining children. CONCLUSION: In the absence of a biological marker, the distinction between ADEM and MS cannot be made with certainty at the time of first presentation, but the authors suggest that a viral prodrome, early-onset ataxia, high lesion load on MRI, involvement of the deep gray matter, and absence of oligoclonal bands are more indicative of ADEM.

Encephalocraniocutaneous lipomatosis (Fishman syndrome): a rare neurocutaneous syndrome.

Encephalocraniocutaneous lipomatosis (ECCL) is a rare congenital neurocutaneous syndrome comprising unilateral cranial lipomas, lipodermoids of the eye and brain abnormalities. A 3-year-old boy who presented at birth with a scalp lipoma and an ipsilateral epibulbar lipodermoid is described. Infantile spasms developed at 9 months of age and cerebral imaging showed thickened and calcified cortex at the right occiput and hemiatrophy of the right hemisphere. These features were consistent with ECCL. Most children with ECCL have significant developmental delay, but we have found that control of seizures was associated with a significant improvement in developmental outcome.

Increased levels of leukemia inhibitory factor mRNA in muscular dystrophy and human muscle trauma.

Leukemia inhibitory factor (LIF) is an important muscle trauma factor both after crush injury and in the mdx mouse dystrophy model. It is important to establish which growth factors have a role in human muscle regeneration due to potential clinical therapeutic applications. As there is limited information concerning LIF expression in human muscle, we investigated the relative levels of LIF messenger ribonucleic acid (mRNA) in human muscle injury. Semiquantitative reverse transcriptase followed by polymerase chain reaction was used to amplify LIF message. We found that although LIF mRNA is expressed in low levels in control muscle, a sevenfold increase occurred after orthopedic muscle trauma and a marked 19-fold increase in dystrophic muscle (P < 0.002). These results indicate that LIF mRNA is upregulated in surgical and especially medical muscle injury with repeated myonecrosis. Muscle growth factors such as LIF may assist in future muscle rehabilitation after injury.

Elevated aminotransferase as a presenting finding in a patient with occult muscle disease.

We report a patient with occult muscle disease who presented with raised serum aminotransaminases. This case report emphasises the importance of considering muscle disease in the differential diagnosis of raised serum aminotransaminases, as it may negate the need for invasive investigations such as liver biopsy.

Benign acute childhood myositis: laboratory and clinical features.

BACKGROUND: Benign acute myositis of childhood is a disorder of midchildhood, typically affecting boys. Symptoms include calf pain and difficulty walking after a viral illness. There is an epidemiologic association with influenza. OBJECTIVES: To describe the clinical and laboratory features of benign acute myositis. RESULTS: Thirty-eight children (32 boys, 6 girls) were seen with 41 episodes of myositis between 1978 and 1997. Two were siblings and three had recurrent episodes. Mean age at onset of symptoms was 8.1 years. Children remained ambulant during 33 of 41 episodes. Two characteristic gaits were noted: toe-walking in 13, with a wide-based stiff-legged gait in another 7. Muscle tenderness was isolated to the gastrocnemius-soleus muscles in 82% of episodes. Recovery occurred within 1 week. Creatine kinase levels were elevated during all episodes. Viral studies were positive in 10 of 24 episodes, 5 because of influenza B. CONCLUSION: Benign acute myositis is a syndrome of midchildhood that can be differentiated from more serious causes of walking difficulty by the presence of calf tenderness, normal power, intact tendon reflexes, and elevated creatine kinase. The gait patterns noted may minimize power generation of the calf muscles by splinting the ankles. Onset in childhood may reflect an age-related response to viral infection, and occurrence primarily in boys may reflect a genetic predisposition or an as-yet unknown metabolic defect.

A fatal case of angiostrongyliasis in an 11-month-old infant.

An 11-month-old boy developed flaccid quadriparesis after two months in Fiji, and was transferred to Australia, where a diagnosis of postinfectious myelitis was made. Despite peripheral blood eosinophilia, eosinophils were not detected in the cerebrospinal fluid, and an infective aetiology was not identified. The patient died of progressive bulbar dysfunction. At autopsy, numerous nematodes, identified as Angiostrongylus cantonensis, were seen in vessels of the lungs, brain and spinal cord, associated with pulmonary abscesses and eosinophilic meningitis. A notable feature was the presence of adult nematodes in the lung.

Bethlem myopathy and engineered collagen VI triple helical deletions prevent intracellular multimer assembly and protein secretion.

Mutations in the genes that code for collagen VI subunits, COL6A1, COL6A2, and COL6A3, are the cause of the autosomal dominant disorder, Bethlem myopathy. Although three different collagen VI structural mutations have previously been reported, the effect of these mutations on collagen VI assembly, structure, and function is currently unknown. We have characterized a new Bethlem myopathy mutation that results in skipping of COL6A1 exon 14 during pre-mRNA splicing and the deletion of 18 amino acids from the triple helical domain of the alpha1(VI) chain. Sequencing of genomic DNA identified a G to A transition in the +1 position of the splice donor site of intron 14 in one allele. The mutant alpha1(VI) chains associated intracellularly with alpha2(VI) and alpha3(VI) to form disulfide-bonded monomers, but further assembly into dimers and tetramers was prevented, and molecules containing the mutant chain were not secreted. This triple helical deletion thus resulted in production of half the normal amount of collagen VI. To further explore the biosynthetic consequences of collagen VI triple helical deletions, an alpha3(VI) cDNA expression construct containing a 202-amino acid deletion within the triple helix was produced and stably expressed in SaOS-2 cells. The transfected mutant alpha3(VI) chains associated with endogenous alpha1(VI) and alpha2(VI) to form collagen VI monomers, but dimers and tetramers did not form and the mutant-containing molecules were not secreted. Thus, deletions within the triple helical region of both the alpha1(VI) and alpha3(VI) chains can prevent intracellular dimer and tetramer assembly and secretion. These results provide the first evidence of the biosynthetic consequences of structural collagen VI mutations and suggest that functional protein haploinsufficiency may be a common pathogenic mechanism in Bethlem myopathy.

Serum antibodies to heparan sulfate glycosaminoglycans in Guillain-Barré syndrome and other demyelinating polyneuropathies.

We tested for serum antibodies to glycosaminoglycans (GAGs), including heparan sulfate, in patients with Guillain-Barré syndrome (GBS) and other disorders. We used ELISA methods that optimize immunoglobulin binding to carbohydrate antigens to measure serum antibodies to heparan sulfate GAGs in GBS, and control neuromuscular and immune disorders. We found serum IgM or IgG antibodies to heparan sulfate GAGs in 34% of patients with GBS. Serum IgM binding to heparan sulfate GAGs was also found in some chronic demyelinating polyneuropathies, with the highest frequency (33%) in patients with IgM anti-MAG M-proteins. Antibodies to heparan sulfate GAGs were rare (1%) in control serums from patients with other disorders. This result is the first demonstration of high titer serum antibodies to a specific antigen in a substantial group of, and with some specificity for, patients with the classically described GBS syndrome of acute-onset, motor-sensory polyneuropathy with demyelinating features.

Congenital muscular dystrophy, white-matter abnormalities, and neuronal migration disorders: the expanding concept.

The congenital muscular dystrophies are a heterogeneous, recessively inherited group of disorders that have been subclassified on the basis of clinical central nervous system involvement. We report two children with "pure" congenital muscular dystrophy, one merosin negative and one merosin positive with extensive white matter and occipital cortical neuromigration abnormalities on magnetic resonance imaging (MRI). The first patient (merosin-negative congenital muscular dystrophy) presented with hypotonia and weakness in the neonatal period and subsequently was found to have a leukoencephalopathy and occipital cortical dysplasia on magnetic resonance imaging. The second patient presented with developmental delay without definite weakness. Initial investigations revealed a leukoencephalopathy and cortical dysplasia, but the patient subsequently was shown to have merosin-positive congenital muscular dystrophy. These patients illustrate that white-matter changes are not specific for merosin-negative congenital muscular dystrophy alone and that extensive cortical abnormality can be found in both groups of patients. In addition, our second patient illustrates a nonmuscular mode of congenital muscular dystrophy presentation that should be considered in patients with a "nonprogressive leukodystrophy."